Iron aluminides are receiving increasing attention as potential high temperature structural materials due to their excellent oxidation and sulfidation resistance. Although the influence of strain rate on the microstructure/property relationships of pure iron and a variety of iron alloys and steels has been extensively studied, the effect of strain rate on the stress-strain and deformation response of iron aluminides remains poorly understood. In this paper the influence of strain rate, varied between 0.001 and 10{sup 4} s{sup {minus}1}, and temperature, between 77 & 1073{degree}K, on the mechanical behavior of Fe-40Al-0.1B and Fe-16.12Al-5.44Cr-0.11Zr-0.13C-1.07Mo-006Y, called FAP-Y, (both in at.%) is presented. Themore » rate sensitivity and work hardening of Fe-40Al and the disordered alloy based on Fe-16% Al are discussed as a function of strain rate and temperature.« less

The majority of the strength characterization studies on ordered intermetallics have concentrated on the assessment of strength and work-hardening at conventional strain rates. Although the influence of strain rate on the structure/property relationships of pure nickel, iron, and titanium and a variety of their alloys have been extensively studied, the effect of strain rate on the stress-strain response of Ni-, Fe-, and Ti-based aluminides remains poorly understood. Dynamic constitutive behavior is however relevant to high speed impact performance of these materials such as during foreign object damage in aerospace applications, high-rate forging, and localized deformation behavior during machining. The influencemore » of strain rate, varied between 0.001 and 10{sup 4} s{sup -1}, and temperatures, between 77 & 800K, on the compressive mechanical behavior of Ni{sub 3}A1, NiAl, Fe{sub 3}Al, Fe-40Al-0.1B, Ti-24Al-11Nb, and Ti-48Al-2Cr-2Nb will be presented. In this paper the influence of strain rate on the anomalous temperature dependency of the flow stresses in these aluminides will be reviewed and compared between aluminides. The rate sensitivity and work hardening of each aluminide will be discussed as a function of strain rate and temperature and contrasted to each other and to the values typical for their respective disordered base metals. 66 refs., 16 figs., 2 tabs.« less

The compressive stress-strain response of three grades of beryllium were studied as a function of strain rate and temperature. Grades S2OOD, E, and F represent a historical perspective of beryllium processing from the 1960`s through 1990`s technology. The purpose of this study was to measure the mechanical behavior of beryllium over a range of deformation conditions for constitutive model development and to obtain microstructural evidence for deformation mechanisms. The compressive stress-strain response was found to be independent of grade and strongly dependent on the applied strain rate between 0.001 and 8000. The strain-hardening response displayed a moderate temperature dependence betweenmore » 77 K and 873 K Because distinct yield was not observed, the intercept-stress from linear strain-hardening fits was analyzed and was found to be only weakly dependent on strain rate and temperature above ambient. Microstructural examination of SHPB specimens revealed that twinning was extensive at strains between 7-22%. A SHPB sample deformed to over 20% strain contained both extensive twinning and grain boundary microcracking.« less

High-strain-rate (2000 s{sup -1}) compression measurements utilizing a specially-designed Split-Hopkinson-Pressure Bar have been obtained as a function of temperature from -55 to +50{degree}C for the plastic-bonded explosive PBX 9501. The PBX 9501 high-strain-rate data was found to exhibit similarities to other energetic, propellant, and polymer-composite materials as a function of strain rate and temperature. The high-rate response of the energetic was found to exhibit increased ultimate compressive fracture strength and elastic loading modulus with decreasing temperature. PBX 9501 exhibited nearly invariant fracture strains of {approximately}1.5 percent as a function of temperature at high-strain rate. The maximum compressive strength of PBXmore » 9501 was measured to increase from {approximately}55 MPa at 50{degree}C to 150 MPa at -55{degree}C. Scanning electron microscopic observations of the fracture mode of PBX 9501 deformed at high-strain revealed transgranular cleavage fracture of the HMX crystals.« less

Compression and tensile measurements were conducted on newly formulated (baseline) and lower molecular weight (virtually-aged) plastic-bonded explosive PBX 9501. The PBX 9501 binder system is composed of nitroplasticized Estane 5703, TM a polyester polyurethane copolymer. The molecular weight of polyester urethanes can degrade with time as a function of hydrolysis, affecting the mechanical behavior of the polymer or a polymer composite material of high explosives, i.e. PBXs. The molecular weight of Estane 5703{trademark} was degraded by exposure to high temperature and humidity for different periods of time, and then formulated to produce ''virtually-aged'' PBX 9501 specimens. Quasi-static and dynamic compressionmore » tests were conducted on the baseline and virtually-aged PBX 9501 as a function of temperature and strain rate. Quasi-static tensile tests were also conducted as a function of temperature and test rate. Rate and temperature dependence was exhibited during both compression and tensile loading. Results also show significant differences between the baseline and virtually-aged specimens for the dynamic compression tests at -15 C, and for the quasi-static compression tests at -15 C, 22 C, and 50 C.« less